False twister

ABSTRACT

Yarn under tension in the draw span of a drawing machine is false twisted by rotation of the yarn by frictionally contacting the yarn with the rims of each of two rotating discs canted with respect to the yarn path.

United States Patent 1191 Bakewell Jan. 1, 1974 [5 FALSE TWISTER 3,535,866 10/1970 Tsurata et a1 57/34 115 3,537,250 11/1970 Mackintosh 57/77.4 [75] Invent David hkewel" 2,936,570 5/1960 Arthur et a1. 57/157 TS 731 Assigneet C m North America, Inc" 3,156,084 11/1964 Van Dijk et al. 57/77.4 Mobile 3,373,554 3/1968 Raschle 57/77.4 2,939,269 6/1960 Dobson 57/77.4 [22] Filed: Aug. 5, 1971 3,287,890 11/1966 McIntosh et a1 57/77.4 3,643,412 2/1972 Maeda et al. 57/77.4 X MP N011 169,175 3,668,853 6/1972 Lang 57 77.4

[52 us. 0. 57/34 11s, 57/77.4, 57/157 TS Primary Examiner-John Pelrakes 1511 1111. c1 D02g 1/02, DOZg 1/08 ArrvmeyDavis. Hoxie. Faithful! & Hapgvod [58] Field of Search 57/34 HS, 51.6, 77.4,

57/77.42, 157 TS, 157 S 57 ABSTRACT Yarn under tension in the draw span of a drawing r113' [56] References Cited chine is false twisted by rotation of the yarn by fric- UNITED STATES PATENTS tionally contacting the yarn with the rims of each of 3,094,834 6/1963 Deeley et a1 57/157 S t t ting di canted with respect to the yarn 3,488,940 1/1970 Mehta 57/157 TS path 3,559,391 2/1971 Rice 57/34 HS 3,066,473 12/1962 Maeda 57/77.4 9 Claims, 3 Drawing Figures FALSE TWISTER The present invention is primarily concerned with imparting a false twist to textile yarns and particularly to a process in which such twist can be imparted as a part of the drawing operation.

Modern synthetic textile materials such as nylon are thermoplastic polymers which are formed into filaments by a procedure in which the polymer is melted and extruded through a spinerette. The hot filaments are pulled from the spinerette through a tube where they are cooled to a firm state. The resulting raw yarn filament is normally wound into packages called cheeses of asize which may represent the product of many hours of extrusion. The raw yarn may be extruded in any of a range .of diameters and may be monoor multifilament. Typically, extrusion occurs at a rate which yields on the order of 1,000 meters of filament per minute.

The raw yarn is later drawn to elongate and reduce the diameter to the ultimately desired denier. Elongation on the order of 300 percent are employed with nylon. The elongation also causes orientation of the molecular structure of the filament for enhanced physical properties.

Presently, it is impractical to draw the yarn concurrently with the extrusion for the 300 percent elongation of filament produced at a rate of 1,000 meters per minute would require dealing with filaments traveling at the impractically high velocity of about 3,000 meters per minute. Consequently, drawing is accomplished as a separate operation using as the supply the extrusion machine cheeses of raw yarn and yielding convenient size pirns or bobbins of drawn yarn. Each extrusion machine cheese yields many filled pirns or bobbins of drawn yarn.

Drawing is accomplished by stretching the raw yarn between a feed roller pair which feeds raw yarn from the supply cheese at a uniform rate and a draw roll having a peripheral speed approximately three times as great as the peripheral speed of the feed rollers. The peripheral speed difference causes the yarn to be stretched and reduced in diameter to the desired size or denier. The yarn in the draw span between the feed rollers and the draw roll may be heated to a softened state to aid in the elongation. One common method of heating the yarn is to wrap one or two turns about a smooth snubber pin which is heated to a desired temperature. Steam, infrared, high frequency energy, or tubular ovens can be employed.

For many uses, it is desirable to create a crimp or undulation in the yarn and various procedures can be employed to this end, including the technique known as false twisting. ln false twisting, twist is imparted to yarn gripped between two points, necessarily yielding S turns on one side of the site of twisting and an equal number of Z turns on the other side. If the twister means were released, the yarn would equalize to an untwisted state. Thus, there is no net twist. By treating the yarn, as by heating and cooling while it is twisted, thus to set the twist, one can give the yarn a permanent memory for the twisted state. When yarn tension is relaxed, the yarn will spring into an undulating shape or crimp. Crimped yarn is particularly useful in knitting stretchable fabrics such as hosiery.

False twisting and setting of the twist'has conventionally been accomplished in an operation subsequent to the drawing operation by specialists known as throwsters. The equipment employed requires unspooling and leading the yarn from the pim through a twisting and setting zone and then respooling the twisted yarn on another pim. The twisting requires apparatus which spins the yarn about its own axis. Commonly, the yarn is run through a tube which isspun by rolling on wheels or belts. It is apparent that the linear speed with which the yarn can progress through the twisting equipment is determined by the limit of the speed at which tube or whatever can be spun and the desired number of twists or turns per inch. High numbers of twists dictate slow linear progress. A further disadvantage of twisting by a separate operation is the unspooling and respooling required.

It has before been proposed to accomplish the desired false twisting while the yarn is in the draw span of the drawing equipment. To do so would eliminate the unspooling, respooling and work scheduling problems implicit in twisting as a separate operation. Further, where heat softening is employed for drawing, that heating will serve for setting of the twist. Yarn twisted as it is drawn is called producer crimp" because the twist is provided by the yarn producer rather than by a texturing specialist such as a throwster.

Several proposals have been made for apparatus for twisting the yarn in the draw span concurrent with the drawing. One general form of such apparatus comprises a funnel shaped entrance to a hollow spindle or armature of a high speed motor. The yarn in the draw span is led through the hollow spindle and guided so as to bear with rolling contact on the funnel mouth. The rolling of the yarn caused by rotation of the funnel manifests as a twist which progresses back toward the heat softened portion of the yarn where the twist is set. Another general form of such draw twisting apparatus uses a rubber flange or tire on the inboard end of the draw roll as is shown in U.S. Pat. No. 3,094,834 to Deeley et al., or a flange on the adjacent separator roller as is shown in U.S. Pat. No. 3,581,487 to Loomes et al. The yarn is guided as it approaches the draw roll so as to cause the yarn to bear with rolling contact with the tire or flange. U.S. Pat. Nos. 2,7l8,l ll and 2,590,374 to Brown teach the imparting of false twist by rolling the yarn on the rim of a rotating wheel or disc. There have been proposed many variations and antecedents of these general fonns of apparatus.

Each has disadvantages which are overcome by the present invention. Primary among the disadvantages of the before proposed draw twisting apparatus is the inability to provide adequate twist rate while maintaining adequate linear draw speed. Several hundred twists per inch are desired while sustaining a linear draw speed on the order of seven hundred to a thousand meters per minute. Attempts at employment of funnel twisters have required resort to special funnel mouthed hollow armature motors operating at around 30,000 r.p.m. Such motors are expensive and require frequent maintenance and rebuilding. Larger funnel diameters theoretically would allow slower motor speeds but the centrifugal force, dynamic balance, and yarn bearing force requirements limit funnel diameters to one or two inches. Desired high twist rates cannot be attained in practice. Similarly, high twist rates cannot be achieved by tires or the like rotating at the speed of the draw roll or the separator roller. That speed is fixed by the equation of draw roll peripheral speed and the linear draw speed. Larger diameter draw roll flanges or tires are impractical because the width allocable to one drawing apparatus in the machine bank is limited by the proximity of the adjacent drawing apparatus in the drawing machine bank.

According to the present invention, yarn under tension in the draw span of the drawing machine is led so as to bear at a first location against the rim of a first rotating disc and thence is led so as to bear at a second location against the rim of a second disc, the discs being canted with respect to the yarn path and located such that the two locations of yarn bearing are generally diametrically opposed. In the preferred embodiment the discs are spaced apart on a common axis and the yarn is led between the confronting faces of the pair of spaced discs which are affixed to the drive shaft of a motor of ordinary type and speed. The rims of the discs are rounded and the axis of the disc pair is canted with respect to the yarn to cause the yarn to bear on the rim of one disc as it enters the space between the discs and to bear on the rim of the other disc as the yarn leaves on its way to the draw roll. The yarn bears against each disc rim with a force sufficient to sustain adequate frictional contact to induce rolling of the yarn as the discs spin. Each disc contributes to the sum of twists. The twisting effect runs back up the yarn into the heat softened portion of the yarn as it leaves the heated snubber pin. The twists are set as the advancing yarn cools. The yarn has cooled enough to be firm when it later contacts the twister discs.

In the drawings:

FIG. 1 is a perspective view of the apparatus of the present invention;

FIG. 2 is an elevational view of the draw span portion of the apparatus; and

FIG. 3 is an edge view of the twister portion of the ap' paratus.

Referring now to the drawings, there is shown a yarn drawing apparatus including the twisting means of the present invention. The drawing machine includes a pair of feed rollers 12 and 14 mounted on shafts 13 and 15 and driven to feed raw yarn from the supply cheese 4 at a feed rate determined by the peripheral speed of the rollers 12 and 14. The yarn is nipped between the rollers for frictional grip. The pinch on the yarn is varied by adjusting the roller spacing. A guide 6 leads the yarn from the supply 4 to the nip of the rollers.

From the feed rollers 12 and 14 the yarn passes around a heated snubber pin 20, through the twisting device 30, to be described in detail below, through a guide 42 to a draw roll 40. In the draw span between rollers 12 and 14 and draw roll 40, the yarn is tensioned and stretched. The yarn is wrapped several times about the draw roll to provide adequate contact with the draw roll to sustain the tension in the yarn in the draw span. The several wraps of yarn about the draw roll are maintained spaced apart by including within the wraps of the yarn a separator roller 50. Separator roller 50 is positioned adjacent to the draw roll 40. The axes 51 of the separator roller and 41 of the draw roll are not parallel, but converge slightly. The wraps of yarn about the draw roll and adjacent separator roller 50 tend to work their way outward along the progressively shorter wrap paths which exist toward the outer ends of the draw roll and separator roller. The result is a progression of each incremental portion of the yarn toward the outer end of the draw roll to provide a spacing between wraps.

The draw roll 40 is driven with a peripheral speed which, for nylon, is approximately thrice that of the feed rollers 12 and 14. Other thermoplastic polymers may require other relative peripheral speeds. The yarn wraps about the draw roll provide a frictional grip about the draw roll to cause the yarn in the draw span to be stretched or elongated about 300 percent for nylon with concomitant reduction in area or diameter. The elongation is assisted by heating the yarn to a soft yieldable state on the temperature controllable electrically heated smooth snubber pin 20.

The drawn and twisted yarn leaves the draw roll 40 and is wound into a conventional package about a pirn 60 by means of a traveler 64 which is a guide arranged in a carrier 62 to revolve about and reciprocate vertically with respect to the pirn to wind the yarn evenly about the pirn.

False twisting is imparted to the yarn by twisting apparatus 30 in the draw span between hot snubber pin 20 and draw roll guide 42. The twisting apparatus 30 comprises a pair of confronting discs 32 and 34 spaced apart slightly and affixed to the drive shaft of motor 36. The motor is conventional. It operates at a conventional speed in the order of 3,600 r.p.m. The discs 32 and 34 are metal and have rounded rim portions 33 and 35 which may be in the form of annular beads of generally semicircular cross-section and preferably are hard chromium plate surfaces polished to a high degree of smoothness. The discs are in the order of 4 to 8 inches in diameter, preferably about 6 inches.

The disc pair is canted, as is best seen in FIG. 3, at an angle a of about 10 to 80, preferably about with respect to the normal yarn path, that is, with respect to the path the yarn would follow but for the disc pair. The incoming yarn first contacts rim 35 of disc 34, diagonally traverses the space between the discs and then contacts rim 33 of disc 32 at a location generally diametrically opposite to the first contact before leaving the twister apparatus. The frictional contact of the yarn with rims 35 and 33 causes the yarn to roll about its own axis as the discs rotate. The yarn contacts each rim but once. The contact extends radially about the surface of the rim. In the device illustrated, the yarn is revolved in the twister and twists are formed below the twister equal in number but opposite in direction to the twists of the yarn above the twister. The yarn coming from the hot snubber pin 20 is softened and the twists appearing in that softened yarn are set as the yarn cools and hardens on its way to the twister. The twist is preserved as a stress in the yarn under tension. When tension is subsequently released as in the fabric knitted from yarn stored on the pirn, the twist causes an undulation or crimp which is realized when the yarn is relaxed. The direction of twist can be changed by reversing the motor 36.

In operation, raw nylon yarn from a cheese 4 is fed at a predetermined rate on the order of 200 meters per minute lineal speed by feed rollers 12 and 14. The yarn is wrapped about a heated snubber pin 20 to soften the yarn and to define the upper limit of the twisting region. The yarn passes between twister discs 32 and 34 spinning at about 3,600 rpm. and bears on rim 35 as it enters and rim 33 as it leaves the twister. The yarn passes through a guide 42 and is wrapped several times about draw roll 40 and separator roller 50. Draw roll 40 is driven at a linear speed on the order of 750 meters per minute. The yarn is then would about pirn 60 by means of a traveler 64. The resulting yarn has a theoretical twist on the order of 300 to 500 twists per inch.

In theory, a single disc would serve to produce the same number of twists per inch as does the disc pair. However, it has been found that two discs are not a redundancy for a single disc will provide only about 60 percent of the actual twists per inch that the dual discs do. The number of twists per inch actually realized is less than the theoretically possible number because of slippage of the yarn in its rolling contact with the disc. Such slippage can be reduced by increasing the force with which the yarn bears against the disc rim but that bearing force is dictated by the yarn draw tension and that tension is fixed by the desired elongation. Therefore, tension cannot be increased as a practical matter. The slippage could be reduced by increasing the coefficient of friction between the yarn and the disc, but other than smooth surfaces cause abrasion of the yarn. The extent of disc radial contact could be increased by using fixed guides to direct the yarn but such guides stop the twist effect and better yarns are produced when the spans in which twists occur are of considerable length and are nearly equal above and below the twister.

The use of two discs doubles the number of contact surfaces and permits greater radial extent for each of the yarn contacts by confining, guiding, and controlling the yarn without resort to nearby twist stopping yarn guides. The two rim contacts each serve as a nearby guide for the other to allow a greater radial extent of contact of the yarn about the curve of the rims. A substantially greater number of twists is actually realized with dual discs than is realized with but one disc.

A further advantage of utilization of a pair of discs is in the control of transverse and lateral deflections of the yarn in the twister. As can be seen in FIG. 3, the yarn is laterally deflected to the right by contact with the back disc 34 and equally to the left by the front disc 32. The yarn on which the twister operates is a span under tension between the hot pin and the lower yarn guide 42. The yarn is rather like a bowstring. If but one disc were employed, for example only the back disc 34, the yarn would be drawn to the right in FIG. 3. The absence ofa draw in the opposite direction provided by the front disc 32 would render the draw to the right less certain in extent. Since there is no nearby guidance or control, the yarn would periodically continue to the right and slip behind the disc ending the twist and spoiling the yarn until an operator discovered the fault and restored proper operation. Furthermore, the absence of front disc 32 would render less certain the radial extent of contact of the yarn in the span with the rim 35 of the single back disc 34 because of inadequate control of transverse bearing of the yarn on the rim. This uncertainty of contact would cause the yarn to periodically slip with respect to the rim and to snap toward center due to yarn tension. The result is a lack of uniformity in twisting. A nearby fixed guide of the sort illustrated as 6 and 42 would reduce these undesirable effects but would determine a twist length in which twisting occurs too short and unequal to the twist length above the twister. The result again would be a lack of twist uniformity and a reduction in actual twists per inch in the finished yarn.

The use of dual discs overcomes these undesirable effects without shortening or unbalancing the length in which twisting occurs. The draw to the right induced by the back disc 34 is opposed by the draw to the left of the front disc 32. The radial extent of contact of back rim 35 is controlled by the proximity of contact with front rim 33 and conversely. Thus, the yarn is constrained and guided transversely and laterally.

While the invention has been described with reference to a preferred embodiment in which the two discs share a common axis in confronting spaced relationship, the invention can employ two or more independent disc axes with the discs arranged longitudinally of the yarn path with their axes canted with respect to the yarn path and their direction of rotation chosen so as to result in additive twisting in the softened portion of the yarn.

I claim:

l. A yarn drawing and twisting apparatus comprising yarn feed roller means to feed yarn at a predetermined rate, a draw roll for elongating yarn under tension in the draw span between the feed roller means and the draw roll, means in the draw span to heat the yarn, and twister means in the draw span between the means to heat and the draw roll, said twister means comprising a pair of spaced parallel discs rotatable together about a common axis, the discs having confronting annular rims with surfaces facing outwardly with respect to the axis for frictionally engaging the yarn, the axis of rotation being canted with respect to the normal path of the yarn in the draw span such that the yarn initially frictionally engages the outwardly facing surface only of the first disc of the pair, generally diagonally traverses the open space between the discs, and, without intervening contact, subsequently frictionally engages the outwardly facing surface only of the second disc.

2. The apparatus of claim 1 wherein the feed roller means comprises a pair of rollers which nip the yarn.

3. The apparatus of claim 1 wherein the means to heat is a temperature controlled heated cylindrical snubbing pin about which the yarn is wrapped.

4. The apparatus of claim 1 wherein the discs of the pair are between 4 and 8 inches in diameter.

5. The apparatus of claim 4 wherein the rim surfaces are smooth hard surface annular beads of generally semicircular cross-section.

6. Apparatus for imparting false twist to a running yarn comprising at least one pair of spaced parallel discs rotatable together about a common axis, the disc having confronting rims with surfaces facing outwardly with respect to the axis for sequentially frictionally engaging the running yarn to cause the yarn to roll about its longitudinal axis, and means to direct the running yarn across the outwardly facing surface only of the rim of one disc, without intervening contact generally diagonally through the space between the discs, and across the outwardly facing surface only of the rim of the other disc.

7. The apparatus of claim 6 wherein the discs of the pair are spaced apart in confronting relationship on a common axis.

8. The apparatus of claim 7 wherein the discs of the pair are between 4 and 8 inches in diameter and the rim surfaces are smooth hard surface annular beads of generally semi-circular cross-section.

9. The method of imparting false twist to a thermoplastic yarn comprising the steps of;

feeding the yarn at a predetermined rate to the draw span of a yarn drawing apparatus,

heating the yarn in the draw span at the entering end establishing frictional contact of the yarn with the thereof, outer surface of the rim of a second disc spaced drawing the yarn by tensioning the yarn in the draw from, confronting and rotating with the first disc span, about the same axis, the yarn generally diagonally establishing frictional contact of the yarn with the traversing the space between the discs outer surface of the rim of a first disc rotating whereby the yarn rolls about its own axis as the discs about an axis canted with respect to the normal rotate and the twist induced by rolling runs back to path of the yarn in the draw span, and without inthe heated portion of the yarn in the draw span.

tervening contact 41V 

1. A yarn drawing and twisting apparatus comprising yarn feed roller means to feed yarn at a predetermined rate, a draw roll for elongating yarn under tension in the draw span between the feed roller means and the draw roll, means in the draw span to heat the yarn, and twister means in the draw span between the means to heat and the draw roll, said twister means comprising a pair of spaced parallel discs rotatable together about a common axis, the discs having confronting annular rims with surfaces facing outwardly with respect to the axis for frictionally engaging the yarn, the axis of rotation being canted with respect to the normal path of the yarn in the draw span such that the yarn initially frictionally engages the outwardly facing surface only of the first disc of the pair, generally diagonally traverses the open space between the discs, and, without intervening contact, subsequently frictionally engages the outwardly facing surface only of the second disc.
 2. The apparatus of claim 1 wherein the feed roller means comprises a pair of rollers which nip the yarn.
 3. The apparatus of claim 1 wherein the means to heat is a temperature controlled heated cylindrical snubbing pin about which the yarn is wrapped.
 4. The apparatus of claim 1 wherein the discs of the pair are between 4 and 8 inches in diameter.
 5. The apparatus of claim 4 wherein the rim surfaces are smooth hard surface annular beads of generally semicircular cross-section.
 6. Apparatus for imparting false twist to a running yarn comprising at least one pair of spaced parallel discs rotatable together about a common axis, the disc having confronting rims with surfaces facing outwardly with respect to the axis for sequentially frictionally engaging the running yarn to cause the yarn to roll about its longitudinal axis, and means to direct the running yarn across the outwardly facing surface only of the rim of one disc, without intervening contact generally diagonally through the space between the discs, and across the outwardly facing surface only of the rim of the other disc.
 7. The apparatus of claim 6 wherein the discs of the pair are spaced apart in confronting relationship on a common axis.
 8. The apparatus of claim 7 wherein the discs of the pair are between 4 and 8 inches in diameter and the rim surfaces are smooth hard surface annular beads of generally semi-circular cross-section.
 9. The method of imparting false twist to a thermoplastic yarn comprising the steps of; feeding the yarn at a predetermined rate to the draw span of a yarn drawing apparatus, heating the yarn in the draw span at the entering end thereof, drawing the yarn by tensioning the yarn in the draw span, establishing frictional contact of the yarn with the outer surface of the rim of a first disc rotating about an axis canted with respect to the normal path of the yarn in the draw span, and without intervening contact establishing frictional contact of the yarn with the outer surface of the rim of a second disc spaced from, confronting and rotating with the first disc about the same axis, the yarn generally diagonally traversing the space between the discs whereby the yarn rolls about its own axis as the discs rotate and the twist induced by rolling runs back to the heated portion of the yarn in the draw span. 